The invention relates to a magnetic-tape apparatus suitable for reading and/or writing information from/on a magnetic tape in tracks which are inclined relative to a longitudinal direction of the magnetic tape, which apparatus has a scanning unit comprising a lower section and an upper section past which the magnetic tape is movable, which scanning unit comprises two magnetic-head units which are rotatable about an axis of rotation and which are movable by means of actuators over an actuating distance from a centre position in two opposite directions parallel to the axis of rotation, both magnetic-head units writing and/or reading one unit of information on the magnetic tape in every revolution of the two magnetic-head units, which unit of information forms an information block which has been or can be recorded on the magnetic tape in a plurality of segments, which segments comprise at least one track each.
The invention also relates to a scanning unit suitable for use in a magnetic-tape apparatus and to a method of reading an information block from a magnetic tape by means of a magnetic-tape apparatus.
Such magnetic-tape apparatuses are used for recording and reproducing inter alia video signals on/from a magnetic tape. During recording the magnetic tape is moved past the scanning unit with a specific tape transport speed, the magnetic-head units recording tracks on the magnetic tape which are inclined at a specific angle relative to the longitudinal direction of the magnetic tape.
A magnetic-tape apparatus and a method of reading an information block from a magnetic tape are known from U.S. Pat. No. 4,314,284. In this known apparatus the magnetic-head units are movable in a direction parallel to the axis of rotation by means of actuators. When the actuators are not activated both magnetic-head units rotate in the same plane and the paths of the magnetic-head units extend parallel to the tracks on the magnetic tape during tape transport with a speed equal to that with which the tracks have been recorded. If these tracks are read in a mode in which the tape transport speed deviates from that during recording the magnetic-head units will follow a path on the magnetic tape which, when the actuators are not activated, is oriented at another angle to the longitudinal direction of the magnetic tape than that parallel to the tracks on the magnetic tape (see FIG. 5). In order to realize tracking in this situation the magnetic-head units are movable from the centre position in two opposite directions parallel to the axis of rotation by means of the actuators (see FIG. 3). A disadvantage of the known apparatus is that the actuating range is not utilized to an optimum extent. In the fast forward or reverse play mode only one half of the actuator range is utilized.